I just don't think it's possible to break up the USA into that many pieces after the Civil War, not without a major global cataclysm. A Yellowstone Eruption might do...
As for a Southern Victory scenario, that is quite easy. The Confederacy could easily break down, especially if the boll weevil hits somewhat earlier and Texas decides to get the hell out of Dodge. The rest of the country could easily split. My favourite idea is where a military coup occurs in the rump USA shortly after the war led by a populist clique of army officers, and a group of politicians flee west, establishing a government in exile in California which eventually evolves effectively into a Californian republic. In between, Deseret breaks off, as does Missouri, which casts itself as a neutral, slaveholding republic between the North and South, making money through river traffic and smuggling all way.